A cellular radiotelephone system consists of a number of base stations and radiotelephone handsets. The user receives and places radiotelephone calls through the handset, which is in radio communication with one of the base stations.
A satellite radio communication system, such as the Iridium system, has a network of satellites, in a low earth polar orbit, that perform the same function as the base stations. These satellites transmit and receive signals from a handset to form a radiotelephone system, allowing users to place radiotelephone calls from anywhere in the world to anywhere in the world.
Unlike cellular systems, the satellites do not remain in the same place with respect to the surface of the earth. Since the satellite could be anywhere in the hemisphere above the user, the radiotelephone's antenna needs to have a gain pattern that covers the hemisphere above the user. Thus, designers have developed an antenna with a hemispherical gain pattern.
A user wishing to place a radiotelephone call needs to have the antenna of the radiotelephone oriented to communicate with any of the possible low earth orbit satellites. As shown in FIG. 5, a radiotelephone handset 10 has an antenna 12 with a hemispherical gain pattern 14. If a user 16 tilts the radiotelephone 10 and therefore the antenna 12, the gain pattern 14 will no longer be aligned with the potential locations of a satellite 18 in the radiotelephone system.
The prior art antenna positioning systems, shown in FIG. 1, orient the antenna 12 in the same plane as the body of the radiotelephone 10. When the user places the radiotelephone's speaker 20 against his ear and the radiotelephone's microphone 22 up to his mouth the antenna 12 naturally tilts at an angle .phi. with respect to vertical. This is undesirable because it causes a rotation of the antenna gain pattern 14 which can result in the radiotelephone not being able to communicate with a satellite 18 near the horizon.
Thus there exists a need for an antenna positioning apparatus that orients the antenna in a vertical position during normal use.